The document introduces Markdown, a lightweight markup language that can be written in plaintext and converted to HTML or rich format. It allows for headings, paragraphs, lists, code snippets, links and images. Markdown is useful for coders to write documentation, blog posts, readme files and in-code comments in an easy to read and write format. Doxygen notation can be used for in-code comments and Markdown files can be automatically generated into documentation with Doxygen. The document provides examples of using Markdown and Doxygen.